SAPOs are molecular sieves which have a three-dimensional microporous framework structure of AlO4, PO4 and SiO4 tetrahedral units.
Microporous silicoaluminophosphate (SAPO) molecular sieves are built of alumina, phosphate and silicate tetrahedral building units. They are manufactured from sources of silicon, such as a silica sol, aluminum, such as hydrated aluminum oxide, and phosphorus, such as orthophosphoric acid. The use of organic templates, such as tetraethylammonium hydroxide, isopropylamine or di-n-propylamine, plays a major role in synthesizing new molecular sieves.
Conventional SAPO-42 is a silica-alumina-phosphate molecular sieve with 3-D intersecting channels and 8 member ring pore openings. The silicon content of SAPO-42 is in the range of about 10-15 wt %. SAPO-42 has cubic morphology with a crystalline size of approximately 1-100 μm. The following organic amines have been identified as a suitable organic template for the synthesis of SAPO-42: diethanolamine with tetramethylammonium hydroxide or fluoride or fluoride and dipropylammonium (DPA), fluoride with crown ethers Kryptofix 22 and Kryptofix 222 (K222). Crystallization of SAPO-42 is performed from 125 to 200° C., and it has a crystallization period, typically of from hours to days.
However, these processes involve several long mixing steps, are difficult to reproduce consistently, and/or use expensive templates such as crown ethers.
Improved SAPO-42 molecular sieves and methods of making them are needed.